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Josh Marvil (CASS)

Josh Marvil Colloquium: Radio Continuum from Local Galaxies

The Australia Telescope National Facility Colloquium
15:00-16:00 Wed 20 Aug 2014

Marsfield Lecture Theatre


Title: Radio Continuum from Local Galaxies

Abstract: I will present the results of a two-part investigation into the radio continuum of
local galaxies, the purpose of which is to better understand how
spectral features are related to physical conditions and star
formation activity. First, I measure the integrated radio spectra for
250 local galaxies and determine that the average shape is better
described by a function with concave curvature than with the standard
power law model. I also investigate relationships between the radio
spectra and other aspects of the sources using a set of radio, far-IR
and optical properties. Second, I form over 30 high-resolution images
of two starbursting galaxies, M82 and NGC 2146, using observations
with the Karl G. Jansky Very Large Array (VLA) at frequencies from 1
to 46 GHz. I detect substantial variations in the radio spectrum
across the face of each galaxy, which I use to demonstrate that the
integrated spectrum is a composite of diverse spectral shapes. I
separate the resolved radio emission into thermal and nonthermal
components and develop a multi-zone description, with
elements including a star-forming disk and galactic wind. I
find evidence for spectral curvature in the synchrotron emission from
these objects, and compare these findings to models of
energy-dependent cosmic ray cooling as well as the predictions from
calorimeter models of the radio-farIR relation. Additionally, I
analyze filamentary emission detected in my very high resolution VLA
image of the galaxy M82 and discuss this emission in the context of
wind outflow channels and magnetic structures.


Alex Hill

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